Apparently, the twist-wire electrode welding machine, marketed by Kobe Steel, Ltd. of Japan, performs brilliantly. Great hopes are pinned on this machine to revolutionize the welding art. All the advantages and limitations of this arc welding machine, and the technique for using it, need not be explored in this disclosure. Apparently, the twist-wire electrode oscillates the arc in the gap formed by the faces of the structures being joined. At least one satisfactory expectation is the elimination of the huge "V"-shaped gap formed by beveling the opposed faces of structures to be joined. Tremendous amounts of weld metal are presently tediously laid down in the "V"-shaped gap to join thick-walled structures. Now, the oscillating arc of the consumed twist-wire electrode distributes the weld metal uniformly between the walls held to a narrow distance apart. However, there is a problem of providing a "bottom" or floor in the narrow gap which will be both electrically conductive and mechanically supportive of the initial pass of the twist-wire electrode.
Obviously, as arc welding is utilized, the structure providing the floor of the gap must be electrically conductive to sustain the arc. At the same time, the mechanical integrity of the bottom or floor structure must be maintained when subjected to the elevated temperature of the welding process. Not only must electrical current between the consumable electrode and work piece be sustained, but the molten metal of the welding bead must be retained by this bottom structure of the gap. In short, the bottom of the gap must be electrically conductive and leakproof.